Is it possible to retrofit conventional buildings with rammed earth?

Assessing the Building’s Suitability

Before attempting to retrofit a conventional building with rammed earth, it’s essential to assess its suitability for this type of construction. This involves evaluating the building’s foundation, insulation, and structural integrity. If the building has a solid foundation, good insulation, and a robust structure, it may be a suitable candidate for rammed earth retrofitting. However, if the building has significant structural issues or lacks adequate insulation, it may be more cost-effective to demolish and rebuild.

Designing the Rammed Earth Retrofit

When designing the rammed earth retrofit, it’s crucial to consider the soil mix, formwork, and thermal mass requirements. A suitable soil mix should be designed to meet the building’s thermal mass needs, typically consisting of a combination of sand, silt, and clay. The formwork should be designed to accommodate the rammed earth mixture, with a minimum thickness of 150mm for optimal thermal mass. In desert and arid climates, it’s essential to use a soil mix with high thermal mass to minimize heat gain during the summer months. A mix of 70% sand, 20% silt, and 10% clay is a good starting point for these climates.

Installation Techniques and Considerations

When installing rammed earth, it’s essential to use specialized equipment, such as a tamper or a hand rammer, to compact the soil mixture. The soil mixture should be poured into the formwork in 50mm layers, with each layer being compacted before the next is added. The walls should be built in sections, with each section being compacted and allowed to dry before the next is added. To ensure a smooth finish, the walls should be plastered with a suitable render, such as a lime-based plaster. In areas with high winds or seismic activity, it’s essential to incorporate additional reinforcement, such as rebar or fiber mesh, into the rammed earth mixture to ensure the structure’s stability.